1. Field of the Invention
The present invention relates to ammunition for small, medium and large caliber guns, and more particularly to a new bullet, notably for hunting guns, having a reduced aerodynamic drag and providing an improved terminal efficiency, in particular in a soft target.
2. Description of the Related Art
Ammunition for the most traditional hunting guns are usually sleeved bullets with a lead alloy core, whose front portion comprises an ogive with a flattened or rounded head. According to a variant, certain bullets have a central channel in the ogive. Thus, U.S. Pat. No. 3,881,421 describes a bullet whose head is hollowed out to cause it to flatten on impact with the target. This ammunition usually has the disadvantage of a high velocity loss on the trajectory and a major loss of mass on impact with the target due to a break-up of the bullet.
Also known are bullets of the same type comprising, on the front end of the ogive, a part made of plastic or other materials intended to improve the aerodynamics of the bullet and the accuracy of the shot, as in patent CH 625043. However, these bullets fragment and expand poorly on impact with the target, which impairs their terminal efficiency.
Application WO 0045120 describes a bullet comprising a broadened base metal core, supporting an envelope with an open ogival head protruding from the central core. U.S. Pat. No. 5,259,320 shows an example of a monometallic lead-free bullet, comprising a central channel situated in the ogive, which has fracture notches intended to control the expansion of the head of the cone and its rolling up in petals, on impact with the target. This technique has the disadvantage of a random expansion, and a risk of fragmentation of the petals formed. In addition, the method of manufacture of this type of bullet by cold stamping causes dynamic imbalances which have the effect of a dispersion of the shots.
The technique of shafted bullet ammunition is today well known. This ammunition comprises a sub-projectile (shaft) stabilized by fins, associated with a sabot (or launcher) having the caliber of the gun, and is described for example in patent FR-A-2.555.728. An enhancement made to this technique is described in patent FR-A-2.795.170 relating to a monometallic bullet with the caliber of the gun or undersize, comprising an internal shaft with a rigidity greater than that of the body of the bullet, disposed along its axis. Bullets of this type are extremely accurate and make it possible to regulate the expansion and retain the mass of the bullet on impact with the target. According to this technique, the diameter of the nose of the ogive represents approximately between 40 and 50% of the maximum diameter of the bullet, which provides it with considerable aerodynamic drag. These bullets are therefore mainly intended for “bush-beating” shooting, over short and medium distances, less than 150 m for rifles and of the order of 50 to 60 m for shotguns. Beyond these distances, and mainly with low initial velocity bullets, the velocity on impact with the target is too low to cause a radial expansion of the body of the bullet that is necessary for satisfactory efficiency.
For “close range” or “stalking” shooting, it is essential to reduce the aerodynamic drag of the bullet on its trajectory, without, for all that, reducing its terminal efficiency.
The precise object of the present invention is to optimize the ballistics of a metal lead-free bullet of the above type to obtain the lowest possible aerodynamic drag on the trajectory while retaining an excellent terminal efficiency on the target while preventing losses of mass of the metal body of the bullet at great distances which may be of the order of 300 m.